textproduct: Quad Cities

KEY MESSAGES

- Semi-organized, lightning-heavy thunderstorms (70-90% coverage) will impact at least locations along and north of U.S. Highway 30 through mid afternoon, with a "worst case" scenario being scattered severe as they do.

- A prolonged period of hot and very humid conditions will be seen starting this afternoon (in the south) and lasting through much of the work week, with peak heat index values upwards to 105 degrees or higher. Extreme Heat Warnings continue for this upcoming hot spell.

- Precipitation chances will remain limited through midweek, increasing each day from Thursday onward. The chance for showers/storms and resultant cloud cover may have an impact on forecast high temperatures as we approach the July 4th weekend.

UPDATE

Issued at 900 AM CDT Sun Jun 28 2026

Persistent MCS from late last night that is approaching northeast Iowa as of mid-morning is our current focus. Radar and 1-minute satellite imagery indicate the most organized and balanced part of this MCS is near the Mason City area as of 9 AM. Motion has generally been due east, although as eluded to in the early morning AFD, the instability gradient does slope east-southeast. In addition, the 40-45 kt low-level jet supporting this as sampled by recent DMX VWP data should continue new storm development and/or festering of existing storms on the southern portion of the MCS. Deep layer shear values of 40-50 kt and MUCAPE of 1,500-2,500 J/kg certainly are enough for a severe threat, but at least some sizable inhibition does exist that may thwart a continuing mature MCS wind threat. That would mean a more isolated wind and hail threat.

So confidence has increased in at least semi-organized / multicell storms in our Iowa CWA north of U.S. Highway 30 between 11 AM and 2 PM. Confidence is lower for south of there, such as toward I-80, as well as into northwest Illinois for early this afternoon. The forecast warm advection near 800 mb remains stout and even with daytime heating, the capping from that warm nose may limit the ability for any new boundary-layer rooted updrafts by early afternoon. That's especially true with the convective debris cloud ahead of this limiting full daytime heating. We'll keep a close eye on it, and have updated PoPs, and some messaging soon for these slight refinements.

SHORT TERM /THROUGH WEDNESDAY NIGHT/

Issued at 235 AM CDT Sun Jun 28 2026

Ongoing MCS acrs southeast SD and far northeast NE looks like it may be going to be a fcst buster for today for at least portions of the local area. Several MCS maintenance parameters and instability/THTA-E gradients bend southeastward and tighten from northwest IA into southeastern to east central IA as the morning progresses. A warm front trying to retreat as well acrs IA all spell trouble with regards to a portion of the MCS propagating east-southeastwrad enough to impact the DVN CWA from late morning into mid afternoon, especially along and north of the I-80 corridor. The extent of shear and building thermodynamic energy support damaging winds to 70 MPH and large hail even if partially elevated. If a sfc root becomes established, LLVL shear/southeast BL flow supports some meso-vortice spin up tornadoes. But all this will be encountering an upper level ridge trying to amplify right acrs the MS RVR Valley as well as building EML between H8-H7 MB which could act as a storm "eater". Several of the latest CAM runs continue to be bullish in maintaining the MCS into our area either along and north of I-80, Hwy 30, or Hwy 20. This while some CAMs and favored deterministic 00z run ECMWF and GFS erode this convection as it arrives or deflects it north of the area in an elevated state.

Have to think/bet on that some of this is going to make it and walked a swath of 20-30 POPs acrs the north half of the DVN CWA from after 15z to 21z or so. Will also go with a NW-to-SE oriented narrow POP swath to account for a connecting elevated warm air advection wing of a linear stripe of broken to isolated showers and possible thunder connecting to the incoming lift of associated MCV.

If this MCS can make it acrs if even in a decaying form, cloud cover/debris/cool outflow looks like it will move acrs at least the Extreme Heat Watch areas. And new Heat Index values for today are marginal in the mid to upper 90s in those areas. Thus have cancelled the EH watch for today and tonight in those areas, and replaced it with an upgrade to an Extreme Heat Warning starting at 17z Monday. More confidence in dry hot conditions with high DPTs to make warning criteria on Monday so as why to make this move now. The rest of the Warning continues as is for now for multi-day Heat Index's of 100- 110, with later shifts assessing the need to extend into the mid or even late week. This depends on cloud debris and edging closer to the western edge of the thermal ridge and ring of fire as early as late Tue and growing in potential Wed through Thu/Fri.

LONG TERM /THURSDAY THROUGH SATURDAY/

Issued at 235 AM CDT Sun Jun 28 2026

Thursday onward through the holiday weekend, we will start to see the strong ridge over the Central CONUS break down a little and start to shift east. This easterly shift will result in upper waves tracking closer/over our area, leading to increasing precipitation chances. Thus, there are uncertainties in the temperature forecast as we approach the July 4th weekend. Overall, we are expected to remain hot and humid. If we avoid the storm track, it is possible that the oppressive heat will continue, but if we fall under the storm track, temperatures may be lower than currently forecast. Currently, precipitation chances are not very high, but we do have 20-40% PoPs each day Thursday onward. Forecast would favor the potential for diurnally driven storms with such hot and humid conditions, with the chance for overnight ring of fire convection that may result in convective debris into the daytime. This convective debris would be a limiting factor on the high temperature forecast.

AVIATION /18Z TAFS THROUGH 18Z MONDAY/

Issued at 1240 PM CDT Sun Jun 28 2026

Primary concerns with the TAFs are MVFR ceilings and nearby thunderstorms through mid afternoon, gusty southeast winds at times this afternoon, and potential for LLWS tonight.

Semi-orgnized thunderstorms will continue to move east-southeast over portions of eastern Iowa and eventually into northwest Illinois through mid-afternoon. While DBQ will see some effects, it is less certain at MLI. If they occur at MLI, they would likely be between 1930-21Z, and probably have some gusts 25-35 kt. Apart from storms, areas of MVFR ceilings are present and will be slow to depart through mid-afternoon. DBQ could even hold onto them through the entirety of the daytime hours.

For winds, east to southeast winds will have regular gusts this afternoon. There are likely to be what we call "wake low" effects at DBQ and possibly CID, which even gustier east- southeast non-thunderstorm winds that occur in the wake of a persistent area of storms. These could result in temporary (~1 hr) gusts to 30-40 kt, but confidence in that is low.

While gusts abate after sunset, sustained winds should hold around 10 kt, maybe higher at times. The setup also favors a 35-40 kt low-level jet AOA 1.5 kft, and that is borderline for true LLWS development given those sustained surface winds. If it occurs atop area airports, 03Z-09Z is the most favored time.

DVN WATCHES/WARNINGS/ADVISORIES

IA...Extreme Heat Warning from noon Monday to 9 PM CDT Tuesday for IAZ040>042-051>054-066. Extreme Heat Warning until 9 PM CDT Tuesday for IAZ063>065-067- 068-076>078-087>089-098-099. IL...Extreme Heat Warning from noon Monday to 9 PM CDT Tuesday for ILZ001-002-007-009-016>018. Extreme Heat Warning until 9 PM CDT Tuesday for ILZ015-024>026- 034-035. MO...Extreme Heat Warning until 9 PM CDT Tuesday for MOZ009-010.